INDIA, Dec. 1 -- India's telecom ministry has instructed smartphone manufacturers to pre-install a government-owned cybersecurity app, Sanchar Saathi, on all new devices, according to a government order.

The app must be installed in a way that prevents users from deleting or disabling it, a requirement that may concern Apple and privacy advocates.

India, one of the world's largest mobile markets with over 1.2 billion subscribers, has seen the app recover more than 700,000 lost phones since its launch in January, including 50,000 in October alone.

The order, dated November 28 and seen by Reuters, requires major smartphone manufacturers, including Apple, Samsung, Vivo, Oppo, and Xiaomi, to ensure the app is preloaded on all new devices w...